Preparation of magneto-sensitive polymer nanocomposite microparticles from copolyesterurethanes via electrospraying

Small stimuli-responsive magneto-sensitivemicroparticles (<5mm) have attracted broad interest for biomedical applications, since they can be delivered minimal-invasively (e.g. via injection) and guided to a specific site or organ,while using their magnetic properties. In addition, such particles can be remotely heated, e.g., for hyperthermia therapy approaches. In this study, we prepared magneto-sensitive polymer-based nanocomposite microparticles by electrospraying of a 1,1,1,3,3,3 hexafluoro-2-propanol solution containing a mixture of a copolyetheresterurethane (PDC) and magnetic Fe₃O₄ nanoparticles (MNPs). Thermal gravimetric analysis (TGA) revealed a weight content of 23±0.5 wt-% MNPs in the PDC magneto-sensitive nanocomposite microparticles, which was identical with the initial starting composition. Scanning electronmicroscopy (SEM) results indicated a bimodal particle size distribution for the prepared magneto-sensitive nanocomposite microparticles around 1.2±0.3mm and 400±100 nm, respectively. Decreasing the size of the magneto-sensitive nanocomposite microparticles resulted in an increase in their reducedmodulus, which was obtained via nanoindentation testing. The PDCmagnetosensitive nanocomposite microparticles could be successfully manipulated in dispersion medium suspension with a permanent magnet, demonstrating their magneto-sensitivity. In addition, the inductive heating capability of the microparticulate nanocomposites could be demonstrated for a thin compression molded test specimen, which could be heated to 44 °C in an alternating magnetic field. The results indicated that such magneto-sensitive nanocomposite microparticles can be potentially used asmagneto-responsive shape-memory microparticles for on-demand and remotely controlled drug delivery.